I. Field of the Invention
The present invention relates to pick-off attachments for multi-spindle machine tools and, in particular, to a pneumatic pick-off attachment for multi-spindle screw machines which provides positive part recovery and increased back-machining capabilities.
II. Description of the Prior Art
Multi-spindle automatic screw machines are widely used in industry for mass producing similar components. Typically, such machines utilize six to sixteen spindles or stations at which the part is subjected to a different machining operation. The stock rotates through each of the stations until completed at which point the part is cut from the bar stock. The individual operations are timed so as to be nearly equal in duration with maintenance of the stock at each station dependent upon the slowest operation having the longest cycle time. As part of the final operation the machined part is cut off from the bar stock fed through the multi-spindle machine. In the past, if additional back-machining of the opposite end of the part is required these operations were conducted on secondary, many times manual, equipment.
Pick-up and back burr attachments have been developed which retrieve the cut-off part and conduct the secondary back machining operations. These attachments employ cam actuated movements which are transferred by linkages requiring numerous settings and adjustments not only during initial set-up but also throughout the run of parts. In the typical prior known cam actuated attachments, adjustments are required for collet tensioning, collet closing, rod stops, ejection rod, quadrant setting, pusher rod clamps, bar stop lever, back-machining cutting tool and back-machining dead stop. In the event even one of these settings is misadjusted it can take an operator several attempts to locate the cause of the misadjustment. Furthermore, the multiple components found in such prior known assemblies depend upon precise setting and synchronous operation. Upon adjusting one setting additional settings may become misadjusted. Often out-of-tune conditions result in lost production parts, broken cut-off tools, broken shear pins and damaged linkage. The cam-operated attachments also may utilize conventional "T" slides and unsealed bearings which are subject to chip contamination and wear. Additionally, limited closing and opening range of the part retrieval collet requires consistency in the outer diameter of the parts. If the parts are oversized, the collet clamping causes the cooperating linkage to become misaligned.
In addition to the alignments and adjustments required for typical attachments, the prior known attachments have limited back-machining capability. In some prior attachments, the bar stop arm is used to retain the back-machining tool. Constant ramming of the bar as it is fed causes the bar stop arm to flex changing the finish depth and center. Furthermore, the limited available machining revolutions due to timing limits the machining depth or overall back machining functions which can be accomplished in the given cycle time. In the past, these limitations were simply accepted as part of cam actuated multi-spindle machines. Any significant back-machining was done as a separate operation typically at a different part of the plant.